System and Method for Providing Secure Mobility and Internet Protocol Security Related Services to a Mobile Node Roaming in a Foreign Network

ABSTRACT

A method for connection roaming a Mobile Node (MN) to a Network GateWay (NGW) for providing secure data path using Internet Protocol (IP) security procedure. Also Mobile IP (MIP) is required for providing mobility to the user, when the MN moves from one sub-network to another. However, when the Home Address of the network is not known, a cyclic interdependency is observed between the IP Security (Ipsec) procedures and MIP procedures. If the home address of the MN is not known initially during the procedure, IPsec Security Associations (SA&#39;s) are formed between the MN and NGW such that only MIP packets are passed through. After the MIP Registration is completed, the Home Address of the MN is known from the MIP registration Reply. MN now forms a data path tunnel with the NGW by exchanging Create_Child_SA messages.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the field of mobile communication. Specifically the invention is about providing mobility services and Internet Protocol related security services simultaneously to a mobile node, which is roaming outside the Home Network. More specifically, this invention provides a system and method to break the cyclic interdependency between IP security messages and Mobile IP messages when the Home Address of the Mobile Node is not known.

2. Description of the Related Art

The invention is related to a system that needs to form an IP security tunnel with the foreign entity (NGW—Network Gateway). The system for the invention (as shown in FIG. 1) comprises of a Mobile Node capable of roaming in foreign networks, Network Gateway (NGW), Foreign Agent (FA) in the foreign network and a Home Agent (HA) in home network. In this invention we assume that the NGW and FA are collocated. The Mobile Node also requires performing the Mobile IP registration for mobility services with Foreign Agent and Home Agent. This invention provides mechanism for the case where the Home Address of the Mobile Node is not known when it is in the foreign network.

Now consider a scenario where the Mobile Node roams to a foreign network that does not provide adequate over the air security. It is to be noted reckon that the Network gateway (NGW) is a trusted entity either in foreign network or in home network and hence provides secure path to any node in the home network. Thus, to provide secure communication channel between Mobile Node and home network it is possible to form an IP security tunnel between Mobile Node and NGW. The present invention makes the Mobile Node capable of roaming while keeping the sessions alive and also provide security to Mobile IP messages even when the Home Address of the Mobile Node is not known.

When the Mobile Node (MN) roams in a foreign network, the Mobile Node forms a tunnel with the Network Gateway (NGW) to obtain Packet Services provided by the network. This can be done for example, to provide secure access over an untrusted interface (e. g. air interface with inadequate security). The local network can provide an IP address to the Mobile Node (Local IP Address routable only up to NGW) while the remote IP address, through which the Mobile Node is accessible to outside world, is to be provided by the external network to which MN is trying to reach for the service (in this case we assume home network obtains the IP address from the external network and sends it to the mobile Node). The scenario is depicted in FIG. 1.

Mobile IP is used for providing mobility services when a mobile roams from one (sub) network to another (sub) network. Mobile IPv4 (Internet Protocol version 4) requires a node in the foreign network acting as a foreign agent, and a node in home agent acting as a Home Agent. When a mobile node roams into a foreign network, it sends a registration request through the Foreign Agent to the Home Agent, indicating that it is available at the given IP address. When the Mobile Node requires a new service, the following procedure is carried out for the establishment of the tunnel between the MN and the PDG (Packet Data Gateway), as shown in the FIG. 3:

1. The IP address of the NGW, which provides the service, is obtained. Then IKEv2 (Internet Key Exchange Protocol version 2) messaging is carried out between the Mobile Node and NGW (with optional authentication). At the end of the IKEv2 signaling a tunnel is formed between the Mobile Node and the NGW that acts as a data path.

2. Once the tunnel is formed Mobile IP Registration request is sent to the Home Agent through FA (Foreign Agent). Then HA sends the Registration reply. If successful, the MN can now securely receive packets destined to it even when it roams in different foreign network. The message flow/sequence is shown in FIG. 3.

Currently in the above scenario, it is not possible to provide IPsec (Internet Protocol Security) and mobility related scenario if the Home Address of the Mobile Node is unknown. This is because the IP security tunnel formation requires the Remote IP Address (Home Address), which is obtained in successful Mobile IP Registration Reply from the Home Agent. There is a cyclic interdependency which prevents the network from providing the Mobile Node with Security and Mobility related services simultaneously. However for MIP Registration Signaling, formation of the tunnel is necessary.

In the light of the foregoing, the invention proposes to provide a method and system for breaking the cyclic interdependency between Mobile IP and IP security. The method for invention comprises of mechanisms for forming a dummy SA when the Home Address of the MN is not known such that only Mobile IP messages are allowed to pass through, making the MIP registration with the Home Agent, and creating the final SA with the NGW when the Home Address is obtained from the MIP Registration Reply (if successful) by creating a child SA.

SUMMARY OF THE INVENTION

It is therefore the primary object of the invention is to provide a system and method for facilitating secure mobility to a mobile node roaming in a foreign network system and whose home address is not known.

It is another object of the invention to break the cyclic interdependency between Mobile IP and IP security so as to enable Mobile IP Registration Signaling and formation of the tunnel.

It is yet another object of the invention to illustrate feature in 3G-WLAN interlocking scenario.

It is also an object of the invention to define the Traffic Selectors and other IKE (Internet Key Exchange) parameters used during the procedure.

Accordingly the present invention unveils a method, which would solve the problems associated with current art, as mentioned below.

1. The Mobile Node forms the tunnel with NGW. (We assume IKEv2 is used to form the secure tunnel here, but can be formed by any other mechanism). The IKE message includes the Traffic Selector for initiator (TSi) as any IP-address (i.e. full range of IP addresses from 0.0.0.0 to 255.255.255.255) and a random port. The Traffic Selector of responder (TSr) is the IP Source address of the Foreign Agent from which the agent advertisement (in the case where the NGW and FA are collocated, TSr contains the NGW IP address and port 434) was sent and port is 434 (standard Mobile IP port). The protocol is UDP.

2. The MIP messages can now be sent through the tunnel and will be passed on the Home Agent. If the MIP registration is successful, the MIP Registration Reply contains the Home Address of the Mobile Node. The mobile node can extract it from the message.

3. Mobile Node now sends the Create Child SA (Security Association) message (of IKEv2) to create the actual SA with NGW using remote IP address (Home IP Address).

The objective herein is to create a dummy SA that encrypts all the traffic going out of the Mobile Node to the NGW. Only the Mobile IP traffic is allowed through the established tunnel initially as the destination port in the SA is set to 434 (or any port on which the MIP application is listening to), which is standard MIP port. However, if two MNs start the initialization process simultaneously, only one of them can proceed as the TS of initiator (TSi) is mentioned as any. However, since the port of MIP is randomized, the probability of one reply being transmitted to the other is negligible.

Accordingly, the present invention comprises a method for establishing mobility and Internet Protocol security related services by a Mobile Node roaming in a foreign network when the Home Address of the Mobile Node is not known, the method comprising the steps of:

(a) forming a secure dummy tunnel with the network gateway for mobile IP passage;

(b) sending the mobile IP messages for registration through the thus formed tunnel to the home agent;

(c) extracting the home address from the successful registration reply message; and

(d) sending a message to create the actual security association with network gateway using the Home IP address to form a data path.

Accordingly, the present invention further comprises a system for establishing mobility and Internet Protocol security related services by a Mobile Node roaming in a foreign network when the Home Address of the Mobile Node is not known.

The other objects, features and advantages of the present invention will be apparent from the detailed description of the invention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the different network elements of the system considered in the invention.

FIG. 2 illustrates the 3G-WLAN interworking system architecture.

FIG. 3 illustrates the sequence for establishing of the IP security tunnel and Mobile IP registration according to the prior art viz. when the Home Address of the MN is known.

FIG. 4 illustrates the sequence for establishing the IP sec tunnel and MIP registration according to the invention i.e. when the Home Address is not known.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A preferred embodiment of the present invention will now be explained with reference to the accompanying drawings. It should be understood however that the disclosed embodiment is merely exemplary of the invention, which may be embodied in various forms. The following description and drawings are not to be construed as limiting the invention and numerous specific details are described to provide a thorough understanding of the present invention, as the basis for the claims and as a basis for teaching one skilled in the art how to make and/or use the invention. However in certain instances, well-known or conventional details are not described in order not to unnecessarily obscure the present invention in detail.

The present invention provides a system and method for providing IPsec and mobility services to the mobile node when the home address of the MN is not known and MN is in foreign network. The subsequent subsections detail the operations done by individual entities to effect the invention.

The procedure for establishing the tunnel connection is as follows. A Mobile Node (MN) connects to external IP network through NGW and MN initiates a Tunnel Establishment Request towards the NGW. MN should create actual SA with NGW when the Mobile IP registration is successfully completed and the Home Address is extracted from the MIP message.

The functions of NGW include:

-   Obtaining the MN information from the tunnel establishment request .     . . -   Passing the obtained information to the AAA-Server (, Authorization     and Accounting server) (to which MN is attached) for authentication     and authorization (Optional).

The NGW also consists of FA functionality in this case as we assume that NGW and FA are collocated.

The functions of Mobile Node include:

-   Identification of NGW for particular service. -   Initiation of Tunnel establishment procedure towards NGW. -   Creation of actual SA with the NGW when the Home Address of the     mobile Node is known

Establishment of Tunnel Between MN And NGW Using Dummy Traffic Selectors

-   1. When a Mobile Node needs to access a service provided by the     network, it needs to form a secure tunnel with a NGW which can     provide the service. The IP address of the NGW can be found by DNS     (Domain Name Server) query or by some other means. -   2. MN initiates a tunnel establishment request with the NGW. As a     part of the tunnel establishment, the user can be authenticated and     authorized for the service. At the end of this procedure the tunnel     is formed between Mobile Node and NGW. The traffic selectors on MN     for ‘out’ direction are as follows: Source IP address is any IP     address (i.e. from 0.00.0 to 255.255.255.255), Port is a randomly     chosen port for the MN. The Destination IP address is the IP address     of the FA (Foreign Agent) through which the Agent Advertisement was     sent (in this illustrative case it is same as PDG address as     obtained in step 1), the port is 434 (or any other port on which     Mobile IP application is listening) and the upper layer protocol is     UDP. -   3. Hence now all the IP packets for the Mobile IP signaling can pass     through the tunnel since the destination port open is the only MIP     port. All other packets are dropped. -   4. [Optional] Mobile Agent Solicitation and Advertisement can be     exchanged. -   5. The Mobile IP Registration Request message is passed through the     tunnel. It is processed normally at FA and forwarded to HA or AAA     (to AAA infrastructure in the case when either Home Agent address or     Home Agent subnet is not known). In the case where the Home Agent     address is not known, the processing of Mobile IP Registration     Request contains the MN-AAA authentication extension, MN-HA Keygen     nonce request (according to IETF internet draft “AAA Registration     Keys for Mobile IPv4” draft-ietf-mip4-aaa-key-*.txt). The HA sends     the Mobile IP Registration Reply and Home Address is contained if     successful. -   6. On receiving the Registration Reply, Mobile Node extracts the     Home Address. Now it creates a new SA between Mobile Node and NGW     with the Home IP address. Thus the data path to the network is     created.

An illustrative example for operating the invention is given here. We consider the scenario where a MN is roaming in a foreign network. The MN needs to connect through IPsec to the trusted node NGW that can be either in foreign network or in home network. The NGW also acts as the Foreign Agent (FA) to the MN. The message flow sequence is as depicted in FIG. 4.

For comparison between the above mentioned system and 3G-WLAN interworking system (http://www.3gpp.org) the PDG acts as a Network Gateway which resides either in the foreign network or in the home network. The 3G-WLAN system is shown in FIG. 2. It consists of:

1. WLAN-UE—to initiate the tunnel.

2. WLAN—For relaying of the EAP signaling between the Home Network and the WLAN UE.

3. PDG: The end-point of the tunnel.

4. AAA Server—is the authenticator which authenticates/authorizes the UE/user.

The Home Agent is assumed to be collocated with GGSN of 3G network for the sake of simplicity, although it is not necessary for this invention to work. The scenario considered here is when the WLAN UE needs to access some service. The UE does not know Home Address and Home Agent Address.

The following steps briefly explain the operation of the system shown in FIG. 1. The procedure for the invention (as shown in FIG. 4) is as follows:

1 and 2. The UE and the NGW negotiate IKE_SA.

3. The UE sends IKE_AUTH request. If the user is to be authenticated and/or authorised it does not include AUTH payload to the NGW. This initiates the authentication procedure. The IDi payload in IKE_AUTH request must contain the NAI (Network Address Identifier) of the MN. Optionally, the MN can attach CERTREQ payload to the IKE_AUTH request if it wants to authenticate the NGW using signature-based authentication. The TSi payload contains 0.0.0.0/0 (indicating full range of IP address from 0.0.0.0 to 255.255.255.255) and a random port through which Mobile IP messages are to be sent. TSr contains the source IP address of the packet containing the Agent Advertisement and the port 434 (or any other predetermined port on which Mobile IP application listens for messages).

4. Authentication and/or Authorization can be carried out between the backend authentication server. If the authentication/authorization is successful, the next steps are carried out.

5. The MN sends IKE_AUTH message, which contains the AUTH payload. The MN can use shared secret, which could be derived during the previous authentication/authorization step.

6. The NGW sends IKE_AUTH response that contains AUTH payload. The NGW calculates the AUTH payload with the shared secret derived during the authentication or any other method.

7. [Optional] MN sends an Agent Solicitation message through the same tunnel. In the 3G-WLAN case, the filtering policy in WAG (Wireless Access Gateway) needs to be changed so that packets from the UE to the All Agent Multicast can be allowed. If the routing policy does not allow the All Agent Multicast packet from UE to NGW, SPD at UE and PDG will contain another entry which will encapsulate all ICMP packets to All Agent Multicast address so that packets can pass through WAG.

8. [Optional] FA sends the Agent Advertisement message in response to the Agent Solicitation.

9. MN sends a MIP_Registration_Req [NAI, MN-HA-Keygen-Nonce-Request, MN-AAA auth ext] with Home Address as 0.0.0.0. The source IP address of the packet is 0.0.0.0 and the destination is the FA IP address (which is same as PDG IP address). Hence the packet is tunneled to the PDG.

10. The FA sends the MIP-Registration-Request to Home Agent, when the Home Agent IP address is known. In case when the Home Agent is not known, the request is sent to AAA infrastructure in appropriate AAA messages format (According to IETF draft [2]). AAA server, after authenticating the MN, generates keys as requested in registration message, and distributes to the respective agents. FA can then forward the Registration Request to the HA, if it has not relayed it earlier. HA then sends the Registration Reply to the FA.

11. The MIP Registration reply is transmitted to the FA either by the HA or indirectly by the AAA server.

12. NGW forwards MIP_REG_REPLY to MN through the established dummy tunnel.

13. MN obtains the Home Address from the MIP_REG_REPLY. Sends CREATE_CHILD_SA request with TSi contain Home address as the IP parameter.

14. NGW Sends Create_Child_SA reply with TSi as remote IP address of MN.

As stated previously, the above procedure can be applied to the 3G-WLAN case, where the Network gateway is PDG, and HA is collocated with GGSN (or is in the same sub-network. The PDG IP address can be discovered in the network by using DNS query over the W-APN (WLAN Access Point Name).

W-APN is the indicative of the service required by the WLAN-UE. The DNS reply contains the list of PDGs capable of providing the given service. The user authentication is carried out by RADIUS/Diameter messages between the PDG and AAA server in the home network.

It will also be obvious to those skilled in the art that other control methods and apparatuses can be derived from the combinations of the various methods and apparatuses of the present invention as taught by the description and the accompanying drawings and these shall also be considered within the scope of the present invention. Further, description of such combinations and variations is therefore omitted above. It should also be noted that the host for storing the applications include but not limited to a computer, mobile communication device, mobile server or a multi function device.

Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are possible and are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart there from. 

1. A method for establishing mobility and Internet Protocol (IP) security related services by a Mobile Node roaming in a foreign network when the Home Address of the Mobile Node is not known, the method comprising the steps of: forming a secure dummy tunnel with a Network GateWay (NGW) for a Mobile IP (MIP) passage; sending mobile IP messages for registration through the secure dummy tunnel to the Home Agent (HA); extracting the Home Address from a successful registration reply message; and sending a message to create an actual Security Association (SA) with the network gateway using the Home Address to form a data path.
 2. The method as claimed in claim 1, wherein the secure dummy tunnel and the MIP registration are synchronously formed by breaking a cyclic interdependency between a requirement of the Home Address IP Security Association and the requirement of IP the Security Association between the Network Gateway and the Mobile Node for transporting the Mobile IP Registration Request messages.
 3. The method as claimed in claim 1, wherein a ‘CREATE_-CHILD_SA message’ of Internet Key Exchange Protocol version 2 (IKEv2) is used to form the actual Security Association for the data path, after obtaining the Home Address from the Mobile IP Registration Reply.
 4. The method as claimed in claim 1, wherein the Mobile Node initiates a tunnel establishment request with the Network Gateway.
 5. The method as claimed in claim 1 wherein the Mobile IP messages are processed at a Foreign Agent (FA) and forwarded to the Home Agent.
 6. The method as claimed in claim 1, wherein the Mobile IP Registration message comprises a Network Access Identifier, a Mobile Node Home Agent key generation nonce, a Mobile Node, and authentication extensions if the Home Agent address and home network prefix are not known.
 7. The method as claimed in claim 5, wherein the Network Gateway relays the Mobile IP Registration Reply to the Mobile Node through the already established tunnel.
 8. The method as claimed in claim 7, wherein Mobile Node extracts the Home Address from the Mobile IP registration reply.
 9. The method as claimed in claim 3, wherein the Mobile Node sends the ‘CREATE_CHILD_SA’ message to the Network Gateway to form an actual Security Association for the data path.
 10. The method as claimed in claim 1, wherein the secure dummy tunnel is established between a Wireless Local Area Network 3^(rd) Generation capable User Equipment (3G WLAN UE) and a Packet Data Gateway over a Wireless LAN Third Generation Mobile System (3GWLAN) interworking system.
 11. The method as claimed in claim 1, wherein the secure dummy tunnel is established between a 3G-WLAN UE and a Packet Data Gateway over a 3G-WLAN interworking system.
 12. The method as claimed in claim 10 wherein the method further comprises: sending an Internet Key Exchange Authentication (IKE_AUTH) request, without AUTH payload to initiate an Extensible Authentication Protocol (EAP) procedure by UE and Traffic Selectors so that only MIP (Mobile IP) messages are allowed to pass; forwarding the EAP success message by Packet Data Gateway (PDG) within the Internet Key Exchange Protocol version 2 (IKE) message to the WLAN-3G capable User Equipment (UE) and forming a dummy tunnel with the UE by sending agreed Traffic Selectors; Solicitation of the Mobile Agent and Advertisement exchanging within the above-formed dummy tunnel; forwarding the MIP Reply Packet Data Gateway to the UE through the dummy tunnel, and; forming the actual SA modifying the existing dummy tunnel by sending the CREATE_CHILD_SA (Security Association) IKEv2 messages.
 13. (canceled)
 14. (canceled) 